Equilibrium and Kinetics Studies of Hexavalent Chromium Biosorption by Luffa Cylindrica using Optimised 1,5-Diphenylcarbazide Method

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 310-317

J. Environ. Treat. Tech.

ISSN: 2309-1185

Journal web link: http://www.jett.dormaj.com

https://doi.org/10.47277/JETT/9(1)317

Equilibrium and Kinetics Studies of Hexavalent

Chromium Biosorption by Luffa Cylindrica using

Optimised 1,5-Diphenylcarbazide Method

Imane Nouacer , Mokhtar Benalia , Ghania Henini , Mebrouk Djedid , Ykhlef Laidani, Chifaa

¹University Amar Telidji-Laghouat, Faculty of Technology, Department Process Engineering, B.P 37G, Laghouat 03000, Algeria

University chlef Faculty of Technology /, Department Process Engineering, Postal address, P.O Box.151.Hay Esslem 02000 Chlef, Algeria

Received: 06/08/2020

Accepted: 23/11/2020

Published: 20/03/2021

Abstract

The Luffa Cylindrica fibers plant have been used as a new biological adsorbent for removal of hexavalent chromium from artificially

contaminated aqueous solutions. The experiments took place in the bath mode. The influence of certain parameters on the adsorption of

chromuim on the biosorbent, namely the adsorbent-adsorbate contact time, the pH of the solution and adsorbent dose of hexavalent

chromium was determined. The kinetic study has shown that the process of adsorption chromuim on luffa cylindrica is a physical process

characterized by its reversibility, by the speed of the establishment of equilibrium. The exploitation of adsorption isotherms using different

classical models of Langmuir, Freundlich and Temkin has shown that adsorption can be governed by the Langmuir model. The maximum

monolayer biosorption capacity of luffa cylindrica was found to be 5.91 mg of chromium /g of LC. The thermodynamic parameters for the

adsorption system were determined at 283, 298 and 313°K. The obtained values showed that the chromium adsorption is a spontaneous and

exothermic process. Finally, the Luffa cylindrica has been evaluated by FTIR, SEM and x-ray diffraction in order to determine if the

biosorption process modifies its chemical structure.

Keywords: Chromium; Biosorption; Isotherms; Thermodynamic; Luffa cylindrica

idea about this danger of pollution. It has turned out that the

Introduction

natural water reserves of certain regions near industrial zones, of

which chromium forms part of their constituents, are

contaminated [4]. Several methods have been used to remove

chromuim such as membrane filtration (ultrafiltration, reverse

osmosis, nanofiltration, electrodialysis), chemical precipitation,

ion exchange and the electrochemical method [5] and

adsorption. The use of coal in the adsorption process is also very

much in demand. Activated carbon has a high adsorption

capacity mainly due to its large specific surface area but this

process remains very expensive. The attention was then focused

on the use of new adsorbents based on abundant natural

materials. Luffa cylindrica, LC, mainly consists of cellulose,

hemicelluloses and lignin; of composition (60%, 30% and 10%

by weight, respectively) [6]. LC has been used as an efficient

adsorbent or as a carrier for immobilization of some microalgal

cells for the removal of water pollutants [7].

The production of industrial and urban wastewater, often

discharged into the receiving environment (sea, rivers and soils)

without prior treatment, causes a degradation of the physic-

chemical and biological quality of this environment by several

pollutants and generates many diseases [1]. As heavy metals

whose density exceeds 5g / cm . These are most commonly

found in the environment as traces: mercury, lead, cadmium,

chromium, copper, arsenic, nickel, zinc, cobalt, manganese [2].

They are characteristic of special chemical properties that make

them toxic to humans as well as to living organisms in the

animal and plant kingdoms. Chromium is one of the most widely

used heavy metals in the industry since it has enough advantages

for tanneries, textile, wood processing and agribusiness. Cr (VI)

is the most problematic form of chromium since in this form

chromium is very toxic and very soluble in water. This solubility

gives it high mobility in ecosystems [3]. Wastewater from some

industries in Algeria contain chromium at levels well above the

standards, such discharges can cause adverse effects on both

aquatic fauna and flora. Some studies in Algeria have given an

The objective of this study is to verify the possibility of

using natural LC as a support for the immobilization of Cr (VI)

ions from the aqueous solution. For this purpose, the various

parameters that control the immobilization of Cr (VI) by the LC

(

solid mass, pH solution, contact time and temperature) were

Corresponding author: Imane Nouacer, University Amar

optimized, followed by a kinetic and thermodynamic study. The

general thrust of this research is to valorize a lignocellulosic

waste as a biosorbent of heavy metals. More specifically, the

Telidji-Laghouat, Faculty of Technology, Department Process

Engineering, B.P 37G, Laghouat 03000, Algeria. E-mail:

i.nouacer@lagh-univ.dz

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Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 310-317

present work aims to study, in an optimization perspective, the

influence of some key parameters on the biosorption capacity of

Cr (VI) by the fibers of Luffa cylindrica, that is very available

and cheap and this from aqueous solutions artificially polluted.

A modeling of the adsorption isotherms and a thermodynamic

study were also carried out in order to understand the nature of

the reaction mechanisms involved during the present biosorption

phenomenon.

an acid medium with

complexing agent, 1,5-

diphenylcarbazide. Thus, a purple-violet complex is formed after

10 minutes and its intensity is measured spectrophotometrically

at 540 nm. The Fourier Transform Infrared Spectroscopy, FTIR

(IRPrestige-21, Shimadzu, Japan) was used to identify the

different chemical functional groups present in the LC. The

analysis was carried out using KBr and the spectral range

varying from 400to 40cm. X-ray diffraction studies were

performed on X-ray diffractometer (Brucker D8 Advance). XRD

studies were carried out using Cu K α radiation, a Ni-filter and a

scintillation counter as a detector at 40 kV and 40 mA on

rotation from 5°to 60° at 2Ө scale. Each sample was finely

powdered into small particle size and homogeneously mixed

before subjecting to X-ray radiation. The morphology of natural

LC was characterized using a scanning electron microscope

Material and methods

.1 Preparation of the biosorbent biomass

The Luffa Cylindrica fibers were manually washed with

distilled water and scrubbed with a brush to remove salts, lime

scale and sediment from the surface. Subsequently, they were

dried in the open air for 24 hours, then in an oven at 40 ° C for

(

SEM) of HIT S2600 N. The powder was deposited on a support

2 mm in diameter after metallization with platinum.

8 hours. The dried leaves were then finely ground (the particle

size between 0.5 and 2 mm), washed again with distilled water,

and then placed in the oven at 80 ° C. for 48 hours until their

weight become constant and then stored in desiccators.

3 Results and discussion

3.1 Luffa Cylindrica powder characterization

.2 Preparation of the chromium (VI) solution

3.1.1 FTIR studies

A Cr (VI) stock solution was prepared by solubilizing a

determined amount of K Cr O in demonized water to obtain a

2 2 7

concentration of 100 mg / L. The other concentrations are

obtained by successive dilutions. The initial pH of the solution

was adjusted by adding diluted solutions to 0.1M HCl or NaOH.

An infrared analysis (FTIR) was performed at the raw LC

and LC-Chromium. By comparing the FTIR spectra of LC

before and after adsorption, there were remarkable shifts in

some bands (Table 1). These bands are the function groups of

LC participate in chromium biosorption, the comparison of the

-1

specters shown in Figure 2 shows. A broad band at 3340 cm

corresponding to the elongation of the OH groups (of shell

.3 Sample Preparation

The Cr (VI) elimination tests were carried out batch wise on

-1

structure and water), a broad band at 2921 cm relating to the

-1

a magnetic stirrer by contacting a synthetic solution of Cr (VI)

with a constant mass of the adsorbent. The solid / liquid

separation of the sample taken is carried out by filtration under

vacuum using a membrane having a porosity of 0.45 μm. For

each filtered sample, the pH and the content of the residual Cr

elongation of the group C-H, a band at 1650 cm which can

very probably relate to the C = C elongations of olefins (alkenes)

and aromatics, very weak bands between 1 392 - 1 506 cm

which are to be put in relation with the CH deformations in the

aliphatic chains and

a wide band between 1000 cm-1

(

VI) were measured. Various tests have been carried out making

characteristic of the deformation in the plane of the aliphatic

CO. The resulting bands may result from the presence of

cellulose, hemicelluloses and lignin, the major constituents of

the shell, as reported by [9], for the Luffa Cylindrica. Note that

the previously described bands are more intense after the

adsorption of Chromium on the Luffa Cylindrica.

it possible to examine the influence of certain parameters on the

elimination of Cr (VI) on the adsorbent, such as the stirring time

(

as the treatment pH (2 to 6). The effect of pH was studied by

buffering the synthetic Cr (VI) solution using the HCl (0.1 N)

and NaOH (0.1N) solutions during the adsorption test. The

removal efficiency of Cr (VI) is calculated by equation (1):

0 to 3 hours) a, the dose of the adsorbent (1 to 20 g / l) as well

(

C_o₋C_e) ∗ 100

C_o

푅(%) =

0 e

Where C and C are the initial and final concentrations of

chromium in the solution in mg/L. The chromium uptake

loading capacity (mg/g) of LC for each concentration of

chromium at equilibrium was determined as [8]:

(

C_o₋C_e). V

푞_푒=

Figure 1: FTIR spectrum of the LC fiber, (a) without adsorbed

chromium (VI), (b) with adsorbed chromium

where Ce is the equilibrium concentrations of the chromium

mg/L) in solution, m is the dose of adsorbent (g/L).

(

.1.2 X-ray diffraction (XRD)

The XRD pattern of LC and LC-Cr (VI) were shown

.4 Analysis

The measurement of the non-adsorbed Cr (VI) concentration

was carried out according to the standard colorimetric method

9]. A sample of 1 ml of the solution is taken which is mixed in

in Figure 2 (a) and (b). The LC at 2θ scale showed peaks at

23.34° and 16.64° with relative intensities of 1145 and 519

respectively. Similarly, LC- Cr(VI) showed peaks at 23.07° and

[

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Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 310-317

6.81° with relative intensities of 883.3 and 465 respectively.

Table 1: FTIR spectral characteristics of LuffaCylindrical

before and after biosorption of chromium

3.1.3 Particle's morphology

Microscopic observation makes it possible to visualize the

morphology of the ground material. Optical microscope analysis

Figure 3(a,b) and scanning electron microscope observations

Figure 4 (a,b) showed that the beams are a continuation of the

vascular system of the stem. The strands or cords that constitute

the net are distributed in a very precise manner forming an

identical skeleton of one type to another.

-1

Transmission band (cm )

Pics

Assignment

FTIR Before adsorption After adsorption

3340

2921

1650

1000

3326

2923

2348

1100

Stretching vibration of OH

Aliphatic C-H group

C=C

C-O

The percentage crystallinity (Xc %) and crystallinity index

(

C.I.) was calculated as follow [10] and [11]:

Xc% = {

} ∗ 100

Ic + Ia

Ic ꢀ Ia

CI =

where IC is peak intensity of crystalline phase, IA is peak

intensity of amorphous phase.The percentage crystallinity

of LC and LC-Cr (VI) fiber was observed as 68.81 and 65.51,

while the crystallinity index as 0.54 and 0.47 It was observed

that the intensity of the peak in LC- Cr (VI) decreased on

adsorption. The decrease in intensity of peak during adsorption

indicated decreased crystallinity of LC- Cr (VI). However;

the LC- Cr (VI) showed broadening of the peak after adsorption

due to convergence of the fibers toward more disordered system

Figure 3: Optical microscope analysis of L.Cylindrica (a) before and (b)

after metal Biosorption

[12]. It has been observed that (Table 2) a slight decreased in

percentage crystallinity of the fiber on adsorption

copolymerization resulted in increase in randomness or disorder

in the crystal lattice of cellulose fiber. This was due to

incorporation of chromium on the active sites of backbone

during adsorption and fibers became more amorphous and

resulted in impaired crystalline structure [13] and [14].

Figure 4: Optical microscope analysis of L.Cylindrica (a) before and (b)

after metal Biosorption

.2 Influence of contact time

The effect of contact time on the Cr (VI) removal rate was

studied over a range of 10 to 180 min with an initial

-1

concentration 50 mg .L , a dose of biosorbent 20 g L at pH2

and at room temperature. The results showed that the

elimination rate increases rapidly during the first 40 minutes,

then increases slowly to 130 minutes, and then remains almost

constant. The results showed that the removal rate of Cr (VI)

was reached at 90 min with 80%, equivalent. The increase of the

elimination rate in the first part could be due to the external

mass transfer which is fast. Then the slow increase in chromium

removal rate to 130 minutes equilibrium time. This means that

there is an internal mass transfer of the adsorbent; this generally

corresponds to a diffusion phenomenon in the internal porosity

of the adsorbent.

Figure 2: X-ray diffraction spectra of LC and LC loaded with Cr (VI)

Table 2: Percentage crystallinity and crystallization index of Lc

and Lc-chromium

Sample

2θ (°)

Intensity

%Xc C.I.

Crystalline

peak

Amorphous

peak

3.3 Influence of pH

The initial pH of the solution is an important parameter that

Lc- (Cr(VI)

23.34

23.07

16.64

16.81

1145 519 68.81 0.54

883.3 465 65.51 0.47

must be considered in any adsorption study. The effect of this

factor on the evolution of the adsorption capacity was analyzed

over a pH range from 2 to 6. The results showed that the

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Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 310-317

maximum amount of Cr (VI) adsorbed occurs at pH 2 with 80%

for an initial concentration of 50 mg / L. The adsorption capacity

decreases sharply when the pH of the solution goes from 2 to 3,

with a rate of adsorption 66 %. Beyond this value of pH, the

adsorption capacity still decreases, but less significantly, to

record its lowest value at pH = 7 with 18%. This behavior is

explained by the fact that at pH = 2, the functional groups

present on the surface of the LC particles (the hydroxyl,

carboxyl, phosphonate and sulphonate groups) undergo a strong

hydronation, which confers on the parietal bio polymers a

positive overall charge. On the other hand, the ionic forms of

hexavalent chromium which may be present in solution are

ꢂ

ꢃ

푒

ꢂ

푞_푡

푘 푞

ꢃ

푞_푒

Or K is the constant relative to this model (g / mg min). The

graphical representation of the variation of the ratio t / Q as a

function of t gives rise to lines Figure 6 from which the

theoretical values K and Qecal are determined, respectively with

the aid of the slopes and disordered at the origin. These values

are presented in Table 4. The correlation coefficients obtained

for the pseudo-second order kinetics model turned out to be the

most significant when a minimum value of 99.3% was recorded

for chromuim concentrations of 10 and 60 mg / L. Moreover,

the Qe values calculated according to the pseudo-second-order

model approach in a very coherent way the values determined

experimentally. Moreover, in most of the adsorption systems

studied, the first-order model and in particular the Lagergren

equation badly correlates the experimental values along the

entire adsorption period and is rather generally applicable during

the first 20 -30 minutes of the adsorption process [15].

The calculated correlation coefficients are closer to unity for the

pseudo-second-order kinetic model than for the pseudo-first-

order kinetic model and the same for theoretical adsorption

capacities that are closer to those obtained experimentally. This

indicates that the experimental results of Cr (VI) adsorption on

LC are well described by the second-order kinetic model.

anionic in nature such as HCrO

, Cr

2 7

, Cr

O10 and Cr

4 13

and this for pH values ranging from 1.5 to 4 [14]. Thus, the

biosorption involved in the present study seems to be mainly due

to an electrostatic attraction phenomenon. In addition, the

adsorption capacity recorded decreases with increasing pH.

Indeed, the higher the pH, the more the solution is concentrated

in free hydroxyl (OH-) radicals which are likely to compete with

the anionic species of Cr (VI) on the active adsorption sites

available on the surface of LC fibers. The same trend towards

the influence of pH on Cr (VI) adsorption has also been reported

for other biological matrices such as A. sydoni [29] and

Rhizopus [30].

.4 Influence of the amount of biomass

Masses of 0.1 to 5 grams of LC were separately contacted

with one liter of 50 mg per 100m L solution of Cr (VI) at pH 2.

The results shows that the amount of chromium adsorbed at

equilibrium increased. Significantly in the weight range

examined. In addition, it is observed that the maximum retention

is obtained for a mass of 20 grams of LC fibers per liter of

solution (rate of adsorption 80% ) and the minimum retention is

observed for a mass of 1 grams of LC (rate of adsorption 11% ).

The increase in the retention rate of hexavalent chromium as a

function of the increase in the biosorbant mass is mainly due to a

consequent increase in the number of active sites of adsorption

on the surface of the Mediterranean biomass.

0.2

0.4

-0.6

0.8

10ppm

20ppm

30ppm

-1.2

1.4

0ppm

T (min)

60ppm

.5 Biosorption Kinetics

In order to study the biosorption kinetics of Cr (VI) on

Figure 5:Pseudo-first order kinetic model for Cr (VI) biosorption onto

crushed LC fibers, Lagergren's first-order and pseudo-second-

order models were used for correlation with the experimental

data. Lagergren's first-order equation [15] reads as follows:

lꢁg(푞 ꢀ 푞 ) = lꢁg 푞 ꢀ 퐾 . ꢂ/2.303

푒

푡

푒

퐼

0ppm

Or Qe and Qt (in mg / g) are the amounts of Cr (VI) adsorbed at

equilibrium and at time t respectively, and K (min ) is the

constant of the Lagergren model. From the log (Qe-Qt) versus t

Figure 5 lines obtained for Cr (VI) biosorption on LC fibers, the

-1

20ppm

30ppm

0ppm

constant and the calculated amount of adsorbed Cr (VI)

(

Qecal) were determined by slope and intersection at the y-axis,

60ppm

respectively (Table 3). It is clear that the Lagergren equation is

not applicable in the case of LC retention on the studied medium

in the range of the studied concentration. In addition, the low

value of the correlation coefficient R² obtained for this model

indicates the poor description of chromium fixation kinetics by

LC. The expression of the second-order model is as follows

T (min)

Figure 6:Pseudo-second order kinetic model for Cr (VI) biosorption onto

[16]:

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Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 310-317

.6 Biosorption isothermes

be 0.6-0.146 for concentration of 10-90 mg/L of chromium.

They are in the range of 0-1 which indicates the favorable

biosorption. These estimated values of R , which are less than

unity, clearly show favorable adsorption of Cr (VI) on LC.

The Freundlich model, which gives an indication of the

heterogeneity at the surface of the adsorbent [20], was applied to

measure the adsorption capacity according to the following

relation:

The LC binding data are processed using the linear

Langmuir, Freundlich, Temkin and Dubinin-Redushkevich

equations. The purpose of this linearization is to be able to

verify the model according to which the adsorption takes place

and to deduce the maximum adsorbed quantities as well as the

affinity of the adsorbate for the adsorbent. The concentration of

chromuim in solution is monitored as a function of time, for the

temperatures 283, 298 and 313 K.

ꢈ

⁄

푛

푞 = 퐾 퐶

퐹

푒

Table 3: Biosorption kinetic model parameters for Cr (VI) by

where K and n are Freundlich constants related to adsorption

capacity and adsorption intensity. The linear Figure 8form of the

Freundlich equation can be written in a logarithmic form

according to the following relation:

Pseudo-ﬁrst order

Pseudo-second

(g/(mg

Chromium

conc. (mg/L)

mg/g)

(min ) R²

R²

(

(mg/g)

min))

lꢁg q_e= lꢁgK + lꢁg C_e

0.23

0.32

0.71

0.92

1.41

0.034

0.029

0.036

0.929 0. 354

0.306

0.103

0.072

0.052

0.997

0.994

0.993

0.864

0.90

0.95

0.94

1.19

1.92

2.5

The Freundlich constants K and n has been determined

from the isotherms and their values are defined as per in Table 5

for the three temperatures. These constants show their influence

on temperature, by the fact that when the temperature increases,

the values of 1 / n decrease which implies a decrease in

adsorption intensity. We also note that the values of 1 / n are less

than unity which indicates favorable adsorption. Since n lie

between 1 and 10, this indicates the physical biosorption of Cr

(VI) on LC.

The Temkin isotherm assumes that the decrease in heat of

adsorption is linear and that adsorption is characterized by a

uniform distribution of binding energies. BL 'The linear form of

the Temkin isotherm is as follows The linear form of the Temkin

isotherm [21] and [22] is as follows:

0.037 0 .993

The Langmuir model makes it possible to determine whether

a monolayer is adsorbed and whether there has been no

interaction between the adsorbed molecules. The Langmuir

equation is valid for only one adsorbed monolayer with a well

defined number of adsorption sites uniform and energetically

identical according to the following relation [19]:

^퐶푒

푙

^푞^ꢄ^ꢅ^x^퐾^퐶ꢆ

푞_푒

1 + 퐾 퐶_ꢆ

퐿

The above can be rewritten to the following linear form:

푅푇

q_e= 푅푇ꢉꢊ 퐾 +

ꢌꢊ 퐶_푒

ꢋ

퐶ꢇ

푞_푚_푎_푥

푏_ꢋ

^푞푒

퐾 푞

퐿

푚푎푥

ꢍꢋ

B = _ꢎ_ꢏ

where, qe is quantity of substance adsorbed on 1 g of luffa

-1

cylindrica (mg.g ). Qm is quantity necessary to cover the entire

-1

where b

J/mol) and K

constants n were obtained from plotting qe versus ln Ce. Values

of b and K are listed in Table 5. The constant Temkin

isotherm in Table 5 shows that the heat of adsorption (B

is the Temkin constant related to heat of biosorption

surface with a monolayer of adsorbed substance (mg.g ). Ce is

(

is the Temkin isotherm constant (L/g). These

-1

concentration of chromuim in solution at equilibrium (mg L ).

is Adsorption energy constant. In order to predict the

efficiency of this adsorption process, dimensionless

can be determined by the

)

equilibrium parameter denoted R

following equation:

decreases with increasing temperature, indicating that the

adsorption is exothermic. The Dubinin-Redushkevich isotherm

(

D-R) is applied to determine the nature of the adsorption

푅_퐿

mechanism based on the theory of potential, assuming that the

surface of the adsorbent is heterogeneous. The linear form of the

isotherm of (D-R) [23]:

(

1 + K_LC_ꢆ)

where K

concentration of chromuim ions. The value of separation

parameter R provides important information about the nature of

is the Langmuir constant and Co is the initial

ꢉꢊ 푞 = ꢌꢊ 푞_푑_ꢀ_훽_휀ꢃ

푒

biosorption. The value of R

isotherm to be irreversible (R

(R = 1) or unfavorable (R >1). The correlation coefficients are

L L

high showing in data in figure 7 good linearity the maximum

adsorption capacities (qmax =5.917 mg/g ) which are very close

to those experimentally calculated and thus the values of R

show the validity of the Langmuir model. The R was found to

indicated the type of Langmuir

=0), favorable (0< R < 1), linear

-1

with q

(mol g ) is the theoretical monolayer saturation capacity

of the adsorbent and ε is the Potential of Polanyi is given as

follows:

ꢈ

휀 = 푅푇ꢉꢊ ꢐ1 +

ꢓ

ꢑꢒ

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Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 310-317

-1

∆푆ꢕ

∆퐻ꢕ

Being R is the gas constant (8.314 J.mol .K )) and T is the

absolute temperature (K). The isothermal constants of qs and B

(

ꢌꢊ 퐾 =

ꢀ _ꢍ_ꢋ

ꢔ

ꢍ

ꢆ

∆

퐺^ꢆ= ∆ꢖ ꢀ푇∆ꢗ

Table4) are obtained from the ordinate and the slope of the Ln

qe curve as a function of ε , respectively. The constant B (mol

푎푠

푎푒

푌푠

푌푒

ꢑ푠

-2

kJ ) gives the average free energy, E (kJ mol-1) of the

adsorption per molecule of the adsorbate when it is transferred

to the surface of the solid of the infinite in the solution and can

be calculated using the following relationship. From the linear

퐾ꢔ =

ꢑ푒

Kc is the adsorption equilibrium constant deduced from the

slope of the graph Ln (Qe) as a function of Ce [25], R is the

constant of perfect gases and T is the temperature in Kelvin. The

calculations were carried out for a temperature range of 283-

313K. The results are shown in Table 5. The negative value of

(ΔH °) obtained indicates that the adsorption process of Cr (VI)

is exodothermic in nature [26].

plot of Dubinin–Radushkevich (D–R) model, q was determined

to 2.5 mg/g, the mean free energy, E= 1.18KJ/mol indicating a

physisorption process. From the data in Table 4, the curves

illustrating the isotherms at 283, 298 and 313 K.show that the

adsorption follows the Langmuir model, the experimental results

can be correlated by the Langmuir equation and the correlation

are close to unity.

Table 4: Langmuir, Freundlicm, Temkin and D-R constants for

Cr (VI) biosorption by LC

Langmuir

Freundlich

Temkin

D-R

T°(K)

max (mg/g)

5.917

5.494

4.926

(L/mg)

0.0648

R²

0.998

0.995

298

313

0.05891

0.05367

1/n

(mg/l)

98K

83K

283

298

313

0.427

0.2377

0.25

0.713

0.703

0.688

0.992

0.989

0.981

(J/ml)

2770

(L/g)

Linear

283

0.9999

0.9998

0.9997

4E-05

3E-05

0.961

0.964

0.939

(313)

2434.98

2191.73

(mg/g)

2.15

0.725

0.787

0.728

Ce (mg/L)

2.27

2.37

Figure7: Langmuir isotherm for Cr (VI)biosorption onto LC at pH2

313

This confirms the previously discussed results which

showed a decreased retention by the elevation of the temperature

of the solution. Also, the relative value of ΔH ° confirms the

idea that the binding of the chromuim molecules to the luffa

cylindrica. Is likely of a physical type. On the other hand, the

value of (ΔS °) indicates the good affinity of the biosorbent with

respect to the Cr (VI)ions and reflects the increase of the

"disorder" factor at the level of the solid interface / solution with

some possible structural changes of the adsorbate and the

biosorbent during the adsorption process. Moreover, the

negative values of (ΔG °) show that the adsorption process

studied is spontaneous [27].

13K

298K

83K

0.5

1.5

0.2

0.4

0.6

LOG (Ce)

Table 5: Thermodynamic parameters of Cr (VI) biosorption onto

LC at different T

Figure 8: Freundlich isotherm for Cr (VI)biosorption onto LC at pH 2

T (K)

∆퐆° (kJ/mol)

-5.347

-5.035

-4.72

∆퐇°(kJ/mol) ∆퐒°(J/mol.K)

.7 Thermodynamic study

The thermodynamic parameters that shall be taken into

-11.293 -0.021

consideration in order to qualify the adsorption processes are

free energy of Gibbs or free adsorption enthalpy ΔG ° (kJ / mol)

due to the transfer of one mole of solute from the solution to the

solid / liquid interface, the adsorption enthalpy; ΔH ° (kJ / mol)

as well as the adsorption entropy; ΔS ° (J / mol / K). These

quantities were calculated according to the following equations

The negative values of the standard enthalpy (ΔH °) (table 5)

confirm that the adsorption of the chromium molecules at the

sites of each adsorbent is of exothermic nature and which is also

indicated by the increase of the adsorbed quantity with the

decrease of the temperature, and that the molecule / particle

interactions are of a physical nature.

[24] and [25]:

∆

퐺^ꢆ= ꢀ푅푇ꢉꢊ퐾푐

315

Journal of Environmental Treatment Techniques

2021, Volume 9, Issue 1, Pages: 310-317

Barkat M, Chegrouche S, Mellah A, Bensmain B, Nibou D,

Boufatit M. Application of Algerian Bentonite in the Removal of

Cadmium (II) and Chromium (VI) from Aqueous Solutions.Journal

of Surface Engi-neered Materials and Advanced Technology.

.8 Comparison of chromium biosorption with different

Biosorbents

The maximum adsorption capacity (qmax) is determined by

the Langmuir model at 303k is compared with other low cost

adsorbents (Table 6). These data show that Luffa cylindrica

achieves good Cr (VI) adsorption results. Significant differences

in the adsorption capacity of Cr (VI) ions can be attributed to

adsorbent properties such as structure, functional groups and

specific surface area. Cr (VI) adsorption on Luffa cylindrica can

be considered as an effective and ecologically advantageous

alternative.

014 ;4, 210-226 .

Dakiky M, Khamis M, Manassra A , Mer'eb M. Selective

adsorption of chromium(VI) in industrial wastewater using low-cost

abundantly available adsorbents . Advances in Environmental

Research .2002 ; 6(4),533-540.

6. Henini G, Laidani Y, Souahi F, Hanini S. Study of static adsorption

system phenol/Luffa cylindrica fiber for industrial treatment of

wastewater .Energy Procedia, 2012; 18,395–403.

Tanobe VOA, Sydenstricker THD, Munaro M, Amico SC. A

comprehensive characterization of chemically treated Brazilian

sponge-gourds (Luffa cylindrica). Polym Test .2005; 24(4), 474–

Table 6: Adsorption capacity of Cr (IV) on various biosorbents

Biosorbent

A. sydoni

Rhizopus

Water lily

Water hyacinth

Green taro

Mangrove leaves

Luffa cylindrica

82.

max

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4.33

6.11

6.61

6.07

6.54

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[28]

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Conclusion

In the present research work, we have studied the

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determination of imipramine, trimipramine and desipramine employing

titanium dioxide nanoparticles and an Amberlite XAD-2 modified glassy

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biosorption capacity of hexavalent chromium by Luffa

Cylindrica fibers that are very available on the Mediterranean

coast, L.cylindrica has been demonstrated that the adsorption

capacity has equilibrium can be optimized by increasing the

amount of biomass, decreasing the temperature, increasing and

fixing the pH of the solution to a value of 2. Isothermal

modeling has shown that the Langmuir model describes

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Cr (VI) on L.cylindrica is a spontaneous, exothermic and

favorable phenomenon. On the other hand, the results of the

kinetic study of the retention show that the chromium is really in

conformity with a kinetics of the second order. This is clearly

confirmed by the values of the correlation factors. Taking into

account all the results provided by this study, the cheap and

fairly available L.cylindrica fibers could be considered as a

promising biological material to be used as an effective

adsorbent for the removal of chromium. (VI) present in the

liquid effluents.

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Acknowledgments

We gratefully acknowledge the university Amar Thelidji

Algeria and university of USTHB for assistance and support of

this work.

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